The present invention relates a valve which consists of a housing provided with a closing opening, a closing member shaped as a part of a ball face which is fitted turnably in the housing and resiliently connected to a pivot shaft, and an annular sealing face.
A valve constructed according to the present invention is in particular suitable for closing the filling opening of a batchwise pulp digester or of a similar pressurized container.
On digesters, for closing the filling opening, lids have been used which are attached to the flange placed at the top of the digester by means of eyebolts and nuts or by a so-called bayonet mount. The use of eyebolts does not permit automation, so that this method has been abandoned. The bayonet mount has been mechanized so as to be controlled from the control room, but it is a drawback of this equipment that the lid cannot be sealed reliably. Chips and other contaminations may remain between the lid and the sealing faces of the digester and cause leakages, in particular so because the internal positive pressure in the digester tends to open the joint.
In view of eliminating these drawbacks, at present, a closing member of the globe valve type is used most commonly. A globe valve can be mechanized easily, and it operates without control, because it is closed reliably, i.e. it is capable of cutting off the feed column in the feed funnel if required, and it is reasonably well sealed, in particular so since the positive pressure in the digester presses the closing member against the seal.
The conventional globe valve constructions which are used as lid valves involve drawbacks which make the valves expensive. For example, the use of a symmetric spherical closing member is expensive owing to the high material and machining costs. In the digesting, chemicals are used which are condensated on colder faces and form hard solid deposits. Owing to the risk of deposits, the sealing member is, as a rule, locked as immobile in order that a deposit that might cause a leakage should not be formed between the seal and the housing. Thereat, the initial surface pressure between the closing member and the closing seal has been produced by means of various so-called tipping devices, which press the closing member against the seal. These additional members cause costs and require servicing. The servicing of a valve of the type described above is difficult and slow at the site of installation, whereby the digester is out of operation and the losses from standstills are high. Nor is it easy to use a replacement valve, for the detaching and installing of the valves and the reconnecting of the various feed, wash, and measurement connections take time.